One of the pilots of the crashed Germanwings Airbus A320 was reportedly locked out of the cockpit as it came down.
Investigators are examining the plane's cockpit voice recorder and it's reported it shows the pilot was unable to return to the cockpit to join his colleague as the aircraft descended over the French Alps.
150 passengers and crew on board the Barcelona to Dusseldorf flight were killed in Tuesday's crash.
Reporter Simon Conway is at Dusseldorf Airport - he says investigators have lots to figure out.
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